Polylactic acid (PLA) resin is a plant-derived resin obtained from plants such as corn, and is biodegradable. It is not derived from petroleum and emits less carbon dioxide gas and suppresses depletion of petroleum-based resources, unlike conventional petroleum-based resins, such as polystyrene resin, polyvinyl chloride (PVC) resin or polyethylene resin, and thus causes less environmental pollution, unlike petroleum-based plastic products. As environmental pollution caused by waste plastics and the like has caused social problems, efforts have been made to expand the application of polylactic acid to various fields, including food packing materials and containers, cases for electronic products, and the like, to which general plastics (petroleum-based resins) have been applied. However, the polylactic acid has poor impact resistance and heat resistance compared to conventional petroleum-based resins, and thus is used in limited applications.
In an attempt to overcome this problem of polylactic acid resin, methods of blending polylactic acid resin with those selected from among conventional petroleum-based plastic resins have been reported. For example, Korean Patent Laid-Open Publication No. 10-2005-0056021 discloses a method of improving the impact resistance of polylactic acid by blending polylactic acid with polycarbonate resin. However, in this case, if the content of polycarbonate resin (petroleum-based plastic resin) is increased in order to improve the impact resistance and heat resistance of polylactic acid, the content of hazardous bisphenol-A in the blend will be increased. As a result, the purpose of use of polylactic acid resin will not be achieved.
In addition, in the case in which polylactic acid resin is blended with a second resin in order to improve the impact resistance and heat resistance, if the second resin has low compatibility with the polylactic acid resin, the impact resistance and heat resistance of the polylactic acid resin can decrease rather than increase, or a blend having desired levels of impact resistance and heat resistance can be difficult to obtain.